"It's too early in the investigation to try to label it. We know it's a vicious act of violence. Obviously, at two Jewish facilities, one might make that assumption, but we're going to have to know more about it," he said.

Suspect Frazier Glenn Cross faces charges of premeditated first-degree murder. He is scheduled to appear in court on Monday, Lt. Craig Buckendahl from the Johnson County Sheriff's Office said.

Photos:Photos: Deadly shootings in Kansas

Photos:Photos: Deadly shootings in Kansas

Deadly shootings in Kansas City suburb – Frazier Glenn Cross, a 73-year-old Missouri man with a long history of spouting anti-Semitic rhetoric, is seen in a police car Sunday, April 13. He is suspected of fatally shooting three people: a boy and his grandfather outside a Jewish community center in Overland Park, Kansas, and a woman at a nearby assisted-living facility.

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Photos:Photos: Deadly shootings in Kansas

Deadly shootings in Kansas City suburb – People gather to mourn the shooting victims April 13 at St. Thomas the Apostle, an Episcopal church in Overland Park. Overland Park is a suburb of Kansas City.

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Photos:Photos: Deadly shootings in Kansas

Deadly shootings in Kansas City suburb – Rachel Trout, 16, receives a hug from a friend after addressing the crowd at St. Thomas the Apostle.

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Photos:Photos: Deadly shootings in Kansas

Deadly shootings in Kansas City suburb – Storm clouds gather over the Jewish Community Center of Greater Kansas City on April 13. It was the site of the first shooting.

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Photos:Photos: Deadly shootings in Kansas

Deadly shootings in Kansas City suburb – Investigators work the scene of a shooting at the Village Shalom Retirement Community in Leawood, Kansas, on April 13.

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Photos:Photos: Deadly shootings in Kansas

Deadly shootings in Kansas City suburb – A police car is seen at the entrance of the Jewish Community Center on April 13.

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Photos:Photos: Deadly shootings in Kansas

Deadly shootings in Kansas City suburb – A Kansas state trooper controls traffic at the entrance of the Jewish Community Center on April 13.

Cop: Elderly shooting suspect in custody

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Video from CNN affiliate KMBC showed a man who appeared to be the suspect sitting in the back of a patrol car and shouting, "Heil Hitler."

Douglass said police are investigating statements the suspect made after his arrest, but declined to provide additional details.

Investigators believe the suspect is affiliated with white-supremacist groups and was involved in previous incidents, such as threats, two federal law enforcement officials told CNN.

The Southern Poverty Law Center, which tracks hate groups, described Cross as a longtime, "raging anti-Semite" who has posted extensively in an online forum that advocates exterminating Jews.

The shootings occurred at the Jewish Community Center of Greater Kansas City in Overland Park, Kansas, and at the Village Shalom Retirement Community in Leawood, Kansas.

Authorities arrested the suspect at a nearby elementary school after the shootings, Douglass said. The suspected shooter is not from Kansas and did not appear to know his victims, he said.

A shotgun was involved in the shootings, Douglass said. Authorities are investigating whether other weapons were also involved.

The gunman shot at a total of five people, Douglass said, but two of them were not injured.

The FBI is at the scene working with local authorities, FBI spokesman Joel Sealer said.

Rabbi Herbert Mandl, a chaplain for the Overland Park Police Department, said the victims included a teenager and an elderly woman.

The shootings, which occurred the day before Passover begins, sound "very much like a hate crime," he said.

"The timing is terrible. The timing is awful," Mandl said. "From what I understand from my contacts, this is a one-person event, and this is hopefully under control now."

The shooting began just after 1 p.m. on Sunday, when gunfire erupted in the Jewish community center's parking lot.

The center was packed with young people participating in weekend activities, like auditions for a singing competition and a rehearsal for a production of "To Kill a Mockingbird," CNN affiliates reported.

"This was a community center full of young teens, and they were on lockdown after the shots started," CNN affiliate KSHB reporter Lisa Benson told CNN. "Some of these kids were taken into locker rooms and told to lay on the floor as the shots rang out."

Jeff Nessel told the Kansas City Star he had just dropped his 10-year-old son off at the community center when a staff member told him to get back inside because there had been a shooting.

"We'll keep you on lockdown. You're safe here," Nessel said a staff member told him.

At the nearby Village Shalom retirement home, Amy Rasmussen was helping with her grandmother's laundry when residents were warned by a staff member.

People "were told by one of the staff that it was a tornado warning ... and stay away from the windows," Rasmussen told the newspaper.

As word of the shooting spread, concerned friends and family came to the facility to check on their loved ones, KSHB reported.

The victims

Two of the victims were a grandfather and grandson who were members of the United Methodist Church of the Resurrection in Leawood, a U.S. congressman said. Rep. Kevin Yoder told CNN the church's minister announced the news during services Sunday night.

"This has been a moment that stunned us all," Yoder said.

Family members said Dr. William Lewis Corporon and 14-year-old Reat Griffin Underwood died as a result of injuries they suffered in the shooting at the Jewish community center.

Corporon "cherished his family, and more than anything had a passion for caring for others."

Reat was high school freshman who "participated in debate, theater and had a beautiful voice. Reat had a passion for life, and touched so many people in his young age," his family said.

U.S. President Barack Obama offered condolences to the victims of shootings and their families.

"I have asked my team to stay in close touch with our federal, state and local partners and provide the necessary resources to support the ongoing investigation," he said in a statement released by the White House. "While we do not know all of the details surrounding today's shooting, the initial reports are heartbreaking."

Shooter's motive unclear

The Anti-Defamation League described the shootings as "an unspeakable and heinous act of violence."

"While it is too early to label these shootings as a hate crime, the fact that two Jewish institutions were targeted by the same individual just prior to the start of the Passover holiday is deeply troubling and certainly gives us pause," the organization said. "We have reached out to local, state and federal law enforcement and stand willing and able to offer guidance and assistance to the community if this incident turns out to have been motivated by anti-Semitism."

The ADL said it warned last week of the increased possibility of violent attacks against community centers during the coming weeks, "which coincide both with the Passover holiday and Hitler's birthday on April 20, a day around which in the United States has historically been marked by extremist acts of violence and terrorism."